1. Field of the Invention
The present invention relates to a hub unit bearing assembly of a kind for use in a wheel bearing having a relatively high load capacity such as, for example, a wheel bearing in a truck or a wagon, and also to a method of making such hub unit bearing assembly.
2. Description of the Prior Art
A vehicle wheel bearing assembly utilizing an angular ball bearing has evolved from the first generation in which a sealed dual bearing is solely utilized, to the second generation in which a hub unit bearing having an outer race concurrently serving as a flanged hub is utilized and then to the third generation in which outer and inner races include respective flanges. The fourth generation is now under development in which an equal-speed joint is integrated with the bearing.
In contrast thereto, the wheel bearing utilizing a tapered roller bearing is generally utilized in a truck and little demand has been made to downscale the wheel bearing and are therefore left behind the times. Under these circumstances, the wheel bearing utilizing the tapered roller bearing has merely evolved to a second-generation hub unit bearing assembly in which the outer race concurrently serves as a flanged hub.
With recent increase in demand for wagons of a type generally known as a one-box car, versatility is desired for and, therefore, integration and downscaling have come to be a prime need. Even a wheel bearing of a high load capacity utilizing a tapered roller bearing is not an exception.
In view of this, attempts have been made to develop the hub unit bearing assembly which may be qualified as a third generation for the wheel bearing of a type utilizing the tapered roller bearing, but because the difference between the tapered roller bearing and the ball bearing leads to a difference in assemblage and, therefore, the third-generation hub unit bearing assembly has not yet been realized.
By way of example, although in the second-generation hub unit bearing assembly in which the tapered roller bearing is utilized, the inner race, the cage or the roller retainer and the rollers can be fitted to the outer race as a prefabricated assembly, the third-generation hub unit bearing assembly requires the hub and the inner race to be mounted on the hub to be assembled at a later stage of assemblage. For this reason, unless the cage is of a shape capable of retaining the rollers as carried thereby, automated assemblage of the hub unit bearing assembly poses a problem.